CRED: Add some configurable debugging [try #6]
Add a config option (CONFIG_DEBUG_CREDENTIALS) to turn on some debug checking
for credential management. The additional code keeps track of the number of
pointers from task_structs to any given cred struct, and checks to see that
this number never exceeds the usage count of the cred struct (which includes
all references, not just those from task_structs).
Furthermore, if SELinux is enabled, the code also checks that the security
pointer in the cred struct is never seen to be invalid.
This attempts to catch the bug whereby inode_has_perm() faults in an nfsd
kernel thread on seeing cred->security be a NULL pointer (it appears that the
credential struct has been previously released):
http://www.kerneloops.org/oops.php?number=252883
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c
index 5573508..36fcabbf 100644
--- a/fs/nfsd/auth.c
+++ b/fs/nfsd/auth.c
@@ -34,6 +34,8 @@
int flags = nfsexp_flags(rqstp, exp);
int ret;
+ validate_process_creds();
+
/* discard any old override before preparing the new set */
revert_creds(get_cred(current->real_cred));
new = prepare_creds();
@@ -86,8 +88,10 @@
else
new->cap_effective = cap_raise_nfsd_set(new->cap_effective,
new->cap_permitted);
+ validate_process_creds();
put_cred(override_creds(new));
put_cred(new);
+ validate_process_creds();
return 0;
oom:
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 492c79b..24d58ad 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -496,7 +496,9 @@
/* Lock the export hash tables for reading. */
exp_readlock();
+ validate_process_creds();
svc_process(rqstp);
+ validate_process_creds();
/* Unlock export hash tables */
exp_readunlock();
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 23341c1..8fa09bf 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -684,6 +684,8 @@
__be32 err;
int host_err;
+ validate_process_creds();
+
/*
* If we get here, then the client has already done an "open",
* and (hopefully) checked permission - so allow OWNER_OVERRIDE
@@ -740,6 +742,7 @@
out_nfserr:
err = nfserrno(host_err);
out:
+ validate_process_creds();
return err;
}
diff --git a/fs/open.c b/fs/open.c
index 40d1fa2..31191bf 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -959,6 +959,8 @@
int error;
struct file *f;
+ validate_creds(cred);
+
/*
* We must always pass in a valid mount pointer. Historically
* callers got away with not passing it, but we must enforce this at